Magnetic sound-reproducing device



April 10, 1928.

Z. JEFFRIES MAGNETIC SOUND REPRODUCING DEVICE Filed 001. 6. 1924 INS H//1 Patented Apr. 10, 1928.

UNITED STATES'PATENT OFFICE.

ZAY JEFFRIES, OF SHAKER HEIGHTS, OHIO, ASSIGNOR TO THE CLEVELAND TRUST COMPANY, TBUSTEEL OF CLEVELAND, OHIO, A CORPORATION OF OHIO.

IAGNETIC SOUND-REPRODUCING DEVICE.

Application filed October 6, 1924. Serial No. 742,078.

and the like.

In such devices, there is usually used a vibrating member responsive to a magnetic field generated by the variable current created, for example, by the amplifying apparm tus of a radio receiving set. The vibrating member is usually a soft iron armature.

I have discovered that a very much more effective reproduction may be accomplished by the use of an armature, as such a vibrat ing member, which will become more magnetic in a given weak magnetic field than soft iron or silicon iron. That is to say, by the use of a certain alloy which reaches saturation in a much lower or less intensified magnetic field than soft iron or silicon iron, I have been able to secure a much higher degree of responsiveness than is possible with the material usually used. After experimenting with such alloys, I have found an alloy of iron and nickel which when used as such a vibrating armature is more responsive to variations in a magnetic field.

In the accompanying drawings. I have illustrated a use of such a vibrating member for loud speaker purposes to which the following description relates. The essential characteristics of this invention are summarized in the appended claims.

In the drawings, Fig. 1 is a perspective view of a magnetic device employing a vibrating member; Fig. 2 is a vertical trans- Verse section through the same; Fig. 3 is a diagrammatic view illustrating the combination of a permanent magnet and the vibrating member actuated by the magnetism of a coil to which the variable current is supplied and shown connected with a sound reproducing means; Fig. 4 is, .an enlarged view of such a vibratingreed.

The particular loud speaker device shown in the drawing is one used for vibrating the stylus needle of a phonograph. It is more fully shown, described, and claimed in the patent of Carl E. Pearson, George Smith and Frank J. Kaehni, No. 1,603,400, issued October 19th, 1926.

Briefly, it consists of a suitable base 1 of bakelite or similar non-conducting and nonmagnetic material from which rises a spoollike projection 3. carrying a magnetic coil 4. Mounted on the base, is a particular form of permanent magnet having a body of punched metal members, the poles of the magnet being similarly formed and consisting of sector-shaped members 12 projecting inwardly, substantially to the center. The vibrating reed 20 extends upwardly therebetween and it is resiliently mounted on a spring member 22 shown as secured to the underside of the base. Asuitable cover 30 is supplied with openings to receive screws for securing it in position.

Referring to the diagram of Fig. 3, it will be seen that when the coil 4 is energized, thereed 20 will become magnetic and as the variable current varies the polarity, the reed will be attracted to one pole 12 and repelled by the other roducing vibration. The vibration of this reed may be caused to produce sound by actuating any suitable diaphragm. I have here shown a phonograph sound box 35 having itsusual stylus needle resting in a notch 22 in the upper end of this reed, whereby the needle 15 caused to vibrate in much the same manner as when operated by the phonograph record. In such a case the reed is so shaped as to be a comparatively stiff member having sufficient body to be effectively acted upon by the magnetism generated by the coil.

Some. ofthe magnetic properties or nickel iron alloys are well known and I am 1:- miliar with-publications prior to this invention giving characteristics of nickel iron alloys with reference to magnetic susceptibility.

For use such as that claimed in this application, howcver, other properties are important.

The nickel iron alloys divide themselves naturally into two groups, namely those containing between about 100% and 75% iron in which the crystal structure at room temperature is that known as body centered cubic and those alloys containing between about nickel and 100% nickel, in which the crystalline structure at room temperature is that known as face centered cubic. It is the latter'class of iron-nickel alloys which are found to be most desirable for the'purposes herein set forth.

Such an alloy which has high magnetic susceptibilit in low strength fields and which reac es magnetic saturation in a weaker field than soft iron or silicon iron may consist of nickel of about 45% and iron about This may be considered an example of suitable proportions for such an alloy for the purposes of this invention. It is an alloy found very satisfactory for use in sound producing means having a magnetic field generated by radio receiving sets such as are now widely used. These proportions, however, are only illustrative and the use of such a material in a sound producing or loud speaker device is not intended to be limited thereto nor do I wish this invention to be limited to any particular physical characteristic of such a vibrating member, nor to the means for creating a magnetic field for actuating it.

preferably of only somewhat less nickel than I In testimony whereof, I hereunto aflix my signature. I

, Y ZAY JEFFRIES. 

